The ambi safety is captured on the right side by either the right grip panel or a slot in the sear pin. First, take the slide and barrel assembly off the frame. With the hammer cocked, grab the left side safety lever and move the safety up a little. You will find a "sweet spot" where the safety will pull straight out. After you get the left side safety off, rotate the right side safety up until the flange clears the grip panel or sear pin then pull it out.
If your safety uses the sear pin for a right side retainer, you might want to replace the pin with a standard sear pin. Not required but it keeps the pin from protruding through the frame.
A new thumb safety may need to be fitted. This is a critical adjustment and if done incorrectly, the safety may not work right. It might not go "on", might not block the sear, or the gun may fire when the safety is switched off.